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Paper: Spectroscopy of Faint White Dwarfs - The DA/DB Ratio and the Initial-Final Mass Relation
Volume: 334, 14th European Workshop on White Dwarfs
Page: 9
Authors: Kalirai, J.S.; Richer, H.B.; Reitzel, D.; Hansen, B.M.S.; Rich, R.M.; Fahlman, G.G.; Gibson, B.K.; von Hippel, T.
Abstract: We present spectroscopic observations of very faint white dwarfs (WDs) in the rich open star cluster NGC 2099 (M37) using both GMOS on Gemini and LRIS on Keck. Of our 24 WD candidates (all fainter than V = 22.4), 21 are spectroscopically confirmed to be bona fide WDs, 4-5 of which are most likely field objects. Surprisingly, all 21 WDs are found to have hydrogen-rich atmospheres (DAs). Based on field WDs with similar temperatures, we would expect four of our objects to have helium-rich atmospheres (DB). We find this to be most likely due to the higher masses of these WDs when compared to the field sample. Hot, high mass WDs may not develop large enough helium convection zones to allow helium to be brought to the surface and turn a hydrogen-rich WD into a helium-rich one. The masses of these WDs are also used to put significant constraints on the initial-final mass relationship. We find that stars with initial masses between 2.8 and 3.4 MSolar lose 75% of their mass through stellar evolution.
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